Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $82.96   13.147%   $93.8668   $93.87   $93.85   $93.90  
  Purchase #2 $226.40   8.576%   $245.8161   $245.82   $245.80   $245.80  
  Purchase #3 $150.39   3.495%   $155.6461   $155.65   $155.65   $155.60  
  Purchase #4 $52.98   10.236%   $58.403   $58.40   $58.40   $58.40  
  Purchase #5 $99.75   7.650%   $107.3809   $107.38   $107.40   $107.40  
  Purchase #6 $223.61   9.163%   $244.0994   $244.10   $244.10   $244.10  
  Purchase #7 $130.48   13.769%   $148.4458   $148.45   $148.45   $148.40  
  7 purchase totals = $966.57       $1,053.6581   $1,053.67   $1,053.65   $1,053.60